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  Subjects -> ENGINEERING (Total: 2258 journals)
    - CHEMICAL ENGINEERING (190 journals)
    - CIVIL ENGINEERING (177 journals)
    - ELECTRICAL ENGINEERING (99 journals)
    - ENGINEERING (1203 journals)
    - ENGINEERING MECHANICS AND MATERIALS (384 journals)
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CHEMICAL ENGINEERING (190 journals)                     

Showing 1 - 0 of 0 Journals sorted alphabetically
AATCC Journal of Research     Full-text available via subscription   (Followers: 3)
ACS Sustainable Chemistry & Engineering     Hybrid Journal  
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 4)
Acta Polymerica     Hybrid Journal   (Followers: 7)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 6)
Advanced Chemical Engineering Research     Open Access   (Followers: 27)
Advanced Powder Technology     Hybrid Journal   (Followers: 12)
Advances in Applied Ceramics     Hybrid Journal   (Followers: 4)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 23)
Advances in Chemical Engineering and Science     Open Access   (Followers: 50)
Advances in Polymer Technology     Hybrid Journal   (Followers: 12)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 6)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 9)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 2)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 7)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 13)
Biofuel Research Journal     Open Access   (Followers: 3)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 11)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 3)
Carbohydrate Polymers     Hybrid Journal   (Followers: 7)
Catalysts     Open Access   (Followers: 6)
ChemBioEng Reviews     Full-text available via subscription  
Chemical and Engineering News     Free   (Followers: 11)
Chemical and Materials Engineering     Open Access   (Followers: 6)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 10)
Chemical and Process Engineering     Open Access   (Followers: 19)
Chemical and Process Engineering Research     Open Access   (Followers: 16)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 32)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 17)
Chemical Engineering and Science     Open Access   (Followers: 13)
Chemical Engineering Communications     Hybrid Journal   (Followers: 11)
Chemical Engineering Journal     Hybrid Journal   (Followers: 26)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 20)
Chemical Engineering Research Bulletin     Open Access   (Followers: 8)
Chemical Engineering Science     Hybrid Journal   (Followers: 19)
Chemical Geology     Hybrid Journal   (Followers: 14)
Chemical Papers     Hybrid Journal   (Followers: 2)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 122)
Chemical Society Reviews     Full-text available via subscription   (Followers: 39)
Chemical Technology     Open Access   (Followers: 11)
ChemInform     Hybrid Journal   (Followers: 4)
Chemistry & Industry     Hybrid Journal   (Followers: 2)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry of Materials     Full-text available via subscription   (Followers: 138)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 5)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal   (Followers: 1)
Coloration Technology     Hybrid Journal  
Computational Biology and Chemistry     Hybrid Journal   (Followers: 9)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 1)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
CORROSION     Full-text available via subscription   (Followers: 19)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 35)
Corrosion Reviews     Hybrid Journal   (Followers: 3)
Crystal Research and Technology     Hybrid Journal   (Followers: 5)
Current Opinion in Chemical Engineering     Open Access   (Followers: 6)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription  
European Polymer Journal     Hybrid Journal   (Followers: 40)
Fibers and Polymers     Full-text available via subscription   (Followers: 4)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 2)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 1)
Gels     Open Access  
Geochemistry International     Hybrid Journal   (Followers: 2)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 3)
Heat Exchangers     Open Access   (Followers: 1)
High Performance Polymers     Hybrid Journal  
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 5)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 9)
Indonesian Journal of Chemical Science     Open Access  
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 9)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 20)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Industrial Gases     Open Access  
Info Chimie Magazine     Full-text available via subscription   (Followers: 3)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 2)
International Journal of Chemical Engineering     Open Access   (Followers: 6)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 2)
International Journal of Chemical Technology     Open Access   (Followers: 5)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access  
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 5)
International Journal of Science and Engineering     Open Access   (Followers: 4)
International Journal of Waste Resources     Open Access   (Followers: 3)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 4)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 5)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 10)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 102)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 10)
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 6)
Journal of Chemical Engineering     Open Access   (Followers: 13)
Journal of Chemical Engineering and Materials Science     Open Access   (Followers: 2)
Journal of Chemical Science and Technology     Open Access   (Followers: 4)
Journal of Chemical Sciences     Partially Free   (Followers: 17)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 10)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 15)
Journal of CO2 Utilization     Hybrid Journal   (Followers: 2)
Journal of Coatings     Open Access   (Followers: 4)
Journal of Crystallization Process and Technology     Open Access   (Followers: 7)
Journal of Environmental Chemical Engineering     Hybrid Journal   (Followers: 3)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Food Processing & Technology     Open Access  
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 4)
Journal of Fuels     Open Access  
Journal of Geochemical Exploration     Hybrid Journal  
Journal of Industrial and Engineering Chemistry     Hybrid Journal   (Followers: 1)
Journal of Information Display     Hybrid Journal  
Journal of Inorganic and Organometallic Polymers and Materials     Partially Free   (Followers: 6)
Journal of Modern Chemistry & Chemical Technology     Full-text available via subscription   (Followers: 2)
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 5)
Journal of Non-Crystalline Solids     Hybrid Journal   (Followers: 7)
Journal of Organic Semiconductors     Open Access   (Followers: 4)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 5)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 4)
Journal of Polymer Engineering     Hybrid Journal   (Followers: 8)
Journal of Polymer Research     Hybrid Journal   (Followers: 6)
Journal of Polymer Science Part C : Polymer Letters     Hybrid Journal   (Followers: 5)
Journal of Polymers     Open Access   (Followers: 2)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Powder Technology     Open Access   (Followers: 1)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 1)
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 234)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Brazilian Chemical Society     Open Access   (Followers: 2)
Journal of The Institution of Engineers (India) : Series E     Hybrid Journal   (Followers: 1)
Journal of the Pakistan Institute of Chemical Engineers     Open Access   (Followers: 1)
Journal of the Taiwan Institute of Chemical Engineers     Hybrid Journal   (Followers: 2)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 8)
Jurnal Bahan Alam Terbarukan     Open Access  
Jurnal Inovasi Pendidikan Kimia     Open Access  
Jurnal Reaktor     Open Access  
Jurnal Teknologi Dan Industri Pangan     Open Access   (Followers: 1)
Korean Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
Main Group Metal Chemistry     Hybrid Journal   (Followers: 1)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 14)
Materials Science and Applied Chemistry     Open Access  
Materials Sciences and Applied Chemistry     Full-text available via subscription  
Molecular Imprinting     Open Access  
MRS Communications     Hybrid Journal  
Nanocontainers     Open Access  
Nanofabrication     Open Access  
Noise Control Engineering Journal     Full-text available via subscription   (Followers: 2)
Ochrona Srodowiska i Zasobów Naturalnych : Environmental Protection and Natural Resources     Open Access  
Petroleum Chemistry     Hybrid Journal   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 3)
Plasma Processes and Polymers     Hybrid Journal  
Plasmas and Polymers     Hybrid Journal  
Polymer     Hybrid Journal   (Followers: 93)
Polymer Bulletin     Hybrid Journal   (Followers: 7)
Polymer Composites     Hybrid Journal   (Followers: 13)
Powder Technology     Hybrid Journal   (Followers: 12)
Recyclable Catalysis     Open Access   (Followers: 1)
Research on Chemical Intermediates     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 5)
Revista Cubana de Química     Open Access  
Revista ION     Open Access  
Revista Mexicana de Ingeniería Química     Open Access  
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Bulletin     Hybrid Journal   (Followers: 2)
Russian Journal of Applied Chemistry     Hybrid Journal   (Followers: 1)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 56)
Solid Fuel Chemistry     Hybrid Journal  
South African Journal of Chemical Engineering     Open Access   (Followers: 2)
South African Journal of Chemistry     Open Access   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 5)
Sustainable Chemical Processes     Open Access   (Followers: 2)
Synthesis Lectures on Chemical Engineering and Biochemical Engineering     Full-text available via subscription  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
The Chemical Record     Hybrid Journal   (Followers: 1)
Theoretical Foundations of Chemical Engineering     Hybrid Journal   (Followers: 2)
Transition Metal Chemistry     Hybrid Journal   (Followers: 2)
Transylvanian Review of Systematical and Ecological Research     Open Access  
Visegrad Journal on Bioeconomy and Sustainable Development     Open Access   (Followers: 1)
Zeitschrift für Naturforschung B : A Journal of Chemical Sciences     Open Access   (Followers: 1)

           

Journal Cover Chemical Engineering Science
  [SJR: 1.178]   [H-I: 114]   [19 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [2969 journals]
  • Compromise between minimization and maximization of entropy production in
           reversible Gray–Scott model
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Wen Lai Huang, Jinghai Li
      In this work, the evolution of entropy production in the Gray–Scott model (P. Gray and S. K. Scott, Chemical Engineering Science 38 (1983) 29–43) is investigated for four representative cases within three regimes. It is revealed that the extremal trends of entropy production for these cases are regime-dependent. In the monostable regime without heterogeneous structures, the steady state follows the minimization of entropy production. For the bistable uniform regime, the steady state with higher entropy production prevails over that with lower entropy production. As to the heterogeneous states that emerge around the bifurcation curves, the entropy production varies in both space and time, showing alternate appearance of states corresponding to minimum and maximum values of entropy production, respectively. The spatiotemporal compromise between maximization and minimization of entropy production appears to govern the corresponding steady states in different regimes.
      Graphical abstract image

      PubDate: 2016-08-19T13:06:16Z
       
  • Nucleation behavior of eszopiclone-butyl acetate solutions from metastable
           zone widths
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Shijie Xu, Jingkang Wang, Keke Zhang, Songgu Wu, Shiyuan Liu, Kangli Li, Bo Yu, Junbo Gong
      Experimental data on the critical supercooling ∆T max, a measure of metastable zone width (MSZWs), as a function of saturated temperature T 0 and cooling rate R were analyzed to describe the nucleation behavior of unseeded eszopiclone-butylacetate solutions. The Nývlt's semiempirical model and Sangwal's theory were employed, respectively. And moreover, we propose a modified model based on the Sangwal's theory in which the nucleation parameters are not dependent on saturation temperature T 0 and nucleation temperature T 1 which can fit the experimental data better than Sangwal's theory. Furthermore, the pre-exponential A and solid–liquid interfacial energy γ can be obtained by employing this modified model, thus, sheds light on the relationship between nucleation parameters and the cooling rate R. Meanwhile, based on the Classical Nucleation Theory, with the estimated interfacial energies from the slope in the modified model, the critical nucleus size and critical Gibbs free energy were calculated and discussed. Then based on the Sangwal's theory, the nucleation activation barrier is found to be dependent on ln R with an exponential relationship, hence, the relationship between nucleation barrier and pre-exponential A can be constructed. At last, the effects of agitation rate and working volume on MSZWs were investigated and discussed.


      PubDate: 2016-08-19T13:06:16Z
       
  • Modeling the change in particle size distribution in a gas-solid fluidized
           bed due to particle attrition using a hybrid artificial neural
           network-genetic algorithm approach
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Amir Abbas Kazemzadeh Farizhandi, Han Zhao, Raymond Lau
      Particle size distribution (PSD) is an important parameter in gas-solid fluidized bed. The change in PSD due to particle attrition can affect the long-term performance of fluidized bed. In this study, artificial neural network (ANN) with genetic algorithm (GA) as a meta-modeling tool was employed to model the change in PSD during fluidization. Experiments were conducted using incineration bottom ash (IBA) as the fluidizing particles and different mass percentage of large and small glass beads were used as the grinding medium. Rosin–Rammler (RR) distribution was used to describe the IBA PSD. The ANN-GA models developed were subsequently used to study the effect of fluidization time, mass percentage of glass beads and size of glass beads used on the IBA particle attrition during fluidization.
      Graphical abstract image

      PubDate: 2016-08-19T13:06:16Z
       
  • Fluid and particle coarsening of drag force for discrete-parcel approach
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Ali Ozel, Jari Kolehmainen, Stefan Radl, Sankaran Sundaresan
      Fine-grid Euler–Lagrange simulations of gas-fluidization of uniformly sized particles have been performed in three-dimensional periodic domains. Snapshots obtained from these simulations have been systematically coarse-grained to extract filter size dependent corrections to the drag law that should be employed in coarse Euler–Euler (EE) simulations. Correction to the drag law that should be employed in Coarse Multi-Phase Particle-in-Cell (MP-PIC) model simulations is examined through a two-step process: separating the coarsening of the fluid and particle phases. It is found that the drag correction is almost entirely due to the coarsening of the fluid cells, with particle coarsening having only a weak effect. It is shown that drag correction for coarse EE and MP-PIC simulations are comparable. As a result, coarse drag models developed for EE simulations can serve as a good estimate for corrections in MP-PIC simulations, and vice versa.
      Graphical abstract image Highlights fx1

      PubDate: 2016-08-19T13:06:16Z
       
  • Practical designs of membrane contactors and their performances in CO2/CH4
           separation
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Seong-Joong Kim, Ahrumi Park, Seung-Eun Nam, You-In Park, Pyung Soo Lee
      Porous polypropylene (PP) hollow fiber membrane contactors operated by either single absorption processes or combined absorption/desorption processes using water have been investigated for use in the production of biomethane from simulated biogas. To observe the effect of operating parameters on the membrane contactors, the connection of modules, flow rates, and operating pressures were tuned. For CO2/CH4 separation, operations using single absorption processes produced a good yield (85%) of high purity CH4 (97%). Connections in series containing two absorption modules facilitated CO2 absorption due to an increase in contact area at the liquid–gas interface. In the combined absorption/desorption processes, CH4 was recovered in 75% yield and 98% purity using two 1″ absorption modules and four 2″ desorption modules connected in series. Although the results were somewhat poorer than those of the single absorption processes due to limits in desorption performance, the combined process provided the potential for producing renewable methane as a fuel for vehicles. Furthermore, for the single absorption processes, the PP hollow fiber membrane contactor was operated continuously, while the membrane used in the combined absorption/desorption processes required periodic maintenance to maintain an acceptable performance.


      PubDate: 2016-08-19T13:06:16Z
       
  • Pyrolysis and catalytic upgrading of low-rank coal using a
           NiO/MgO–Al2O3 catalyst
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Yi Li, Muhammad Nadeem Amin, Xingmei Lu, Chunshan Li, Fuqiang Ren, Suojiang Zhang
      The catalyst NiO/MgO–Al2O3 was prepared by loading magnesium and nickel onto the surface of γ-Al2O3 beads, respectively, and was adapted to in situ upgrade the high temperature pyrolysis vapor derived from coal pyrolysis. The catalyst synthesis process, and structural variation were characterized by the XRD, SEM, and physical adsorption analyzer. In order to examine the catalytic effect on the different nickel loading ratio in the catalysts, the solid–liquid–gas product distribution, variation of gas and components of coal tar were studied by simulated distillation, GC/MS, elemental analysis and so on. The results shows both the tar yield and the content of the light fraction in the tar can be increased by catalytic up grade. The catalyst has a strong ability to convert the heavy component and polycyclic aromatic hydrocarbons in the tar to lower molecular weight components.


      PubDate: 2016-08-19T13:06:16Z
       
  • Kinetic investigations of the steam reforming of methanol over a
           Pt/In2O3/Al2O3 catalyst in microchannels
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): M. Wichert, R. Zapf, A. Ziogas, G. Kolb, E. Klemm
      A kinetic study of methanol steam reforming over bimetallic Pt/In2O3/Al2O3 catalyst was carried out. The kinetic measurements were performed in a microstructured monolithic reactor with an external recycle free of temperature and concentration gradients. By the help of residence time distribution measurements it could be verified that the reactor showed the behaviour of an ideal continuous stirred tank reactor (CSTR). The absence of external and internal concentration gradients could be proven by corresponding experiments and theoretical diagnostic criteria. The kinetic measurements performed by variation of the reactant inlet partial pressures revealed that in the temperature range from 310°C to 355°C the molar rate of methanol consumption mainly depends on the methanol partial pressure, especially at higher temperatures, whereas there is only minor dependence on the water partial pressure. Carbon dioxide has no inhibiting effect, whereas hydrogen showed a weak inhibiting effect. Two power laws and three Langmuir-Hinshelwood rate equations were created for the modelling of the kinetic data. Power laws could not be fitted to the measured values. Therefore the uses of Langmuir-Hinshelwood rate laws with temperature dependent sorption constants are inevitable for the modelling. The model discrimination revealed that the rate law derived from a mechanism, which assumes the dehydrogenation of an adsorbed methoxy-species as rate determining step, described the measured kinetic data second best. Optimum agreement between observed and predicted molar rates of methanol consumption was obtained when applying a Langmuir-Hinshelwood rate law assuming dissociative methanol and molecular water adsorption on the catalyst surface. Dissociative adsorption of water and methanol at the same active site may be excluded. This leads to a better evaluation of the models that assume molecular water adsorption at the same site where methanol ties or the ones with no participation of water in the rate determining step (RDS) under discrimination.


      PubDate: 2016-08-19T13:06:16Z
       
  • Mean penetration depth of metals in hydrodemetallation catalysts
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Loïc Sorbier, Frédéric Bazer-Bachi, Maxime Moreaud, Virginie Moizan-Basle
      A descriptor has been proposed, the mean penetration depth, to characterize the deposit profiles of metals in hydrodemetallation catalysts. This mean penetration depth can be obtained from concentration maps or profiles of elements along catalyst cross sections using local characterization techniques. This descriptor is well suited even for very irregular shapes such as multilobed extrudates often encountered in industrial catalysts. Using a very simple model of metal deposit, the mean penetration depth can be analytically related to the Thiele modulus of the deposit reaction and consequently to the catalyst efficiency for trivial shapes (infinite slab, infinite cylinder and sphere). The mean distance to the surface of the catalyst pellet is found to be the convenient quantity to renormalize Thiele modulus and mean penetration depth to obtain an universal curve independent of the catalyst pellet shape. An example of application is given on a used hydrodemetallation catalyst of tetralobed shape.
      Graphical abstract image Highlights fx1

      PubDate: 2016-08-19T13:06:16Z
       
  • Experimental and computational study of a high speed pin mixer via PEPT,
           visualization and CFD
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Anne K. Konz, Erich Windhab
      Continuous high speed pin mixers have been successfully implemented industrially to mix high fractions of powders into highly viscous non-Newtonian liquids. However, they have not been described in the literature yet. This work presents a multi-method approach, consisting of conventional torque and throughput measurements to calculate average residence times and dimensionless Reynolds/power numbers for suspension mixing, Positron Emission Particle Tracking (PEPT) to gain information on particle trajectories and velocities in the investigated opaque model system, high speed film visualization and CFD simulations. By the combination of these methods, valuable information on the influence of variable process parameters, particularly on the influence of pin configuration, pin shape and inclination of semi-cylindrical pins on mixing mechanisms and efficiency, could be gathered for a broad range of viscosities and powder fractions in Newtonian and non-Newtonian fluids. Flow patterns such as a “Split-and-Recombine” convection pattern at the pins, axial mixing mechanisms and beneficial process conditions to reduce particle sedimentation caused by centrifugal forces in the mixer were retrieved from the results. The PEPT methodology was successfully implemented for a high-shear continuous mixing process of suspensions for the first time. As the combined methodology shows reasonable and reliable results that were also applicable at industrial scale, the work provides sound basis for further research development of measurement techniques for other mixing processes, especially in opaque systems.


      PubDate: 2016-08-19T13:06:16Z
       
  • Pressure drop across stainless steel fiber sintered felts with honeycombed
           channels
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Jun Deng, Zhenping Wan, Rui Cao
      A novel catalyst support for volatile organic compound elimination—stainless steel fiber sintered felt with honeycombed channels (SSFSFHC)—is prepared via solid phase vacuum sintering. The SSFSFHC is composed of a three-dimensional reticulated skeleton, irregular open pores and interconnected parallel channels. The surfaces of the stainless steel fibers are rough and characterized by laminar and jagged structures. The influence of the honeycombed channels on the pressure drop across the SSFSFHC is experimentally analyzed. Experimental results indicate that the pressure drop mainly depends on the channel occupied area ratio. This kind of rough stainless steel fiber sintered felt (SSFSF) exhibits a higher inertial coefficient and high permeability compared with smooth SSFSF and foam materials. The correlations of the pressure drop for SSFSFHCs are established, and a structural factor is proposed to characterize their geometric features. In addition, a surface morphology strengthened factor is suggested for the characterization of the influence of the rough surface morphologies of the fibers on the inertial coefficient. Finally, a statistical analysis of the correlations is conducted to prove the significance of the correlations.


      PubDate: 2016-08-19T13:06:16Z
       
  • Ceramic block packing of Honeycomb type for absorption processes and
           direct heat transfer
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Rumen Darakchiev, Simeon Darakchiev, Daniela Dzhonova-Atanasova, Svetoslav Nakov
      Ceramic block packing of Honeycomb type has been developed and studied for the purpose of absorption and heat transfer processes in column apparatuses. The packing design ensures high efficiency at relatively low pressure drop. The packing is easy to manufacture and the ceramic is resistant to high temperatures and chemically aggressive environments. Detailed studies on the characteristics of mass transfer and fluid flow have resulted in development of a reliable methodology for design of packed columns for absorption processes and direct heat transfer. Their successful implementations in the chemical industry, for environmental protection, and in the power production have confirmed the validity of the methodology. The Honeycomb packing is used in an industrial system for purification of process gases from H2S in staple cellulose fiber production, which operates with a degree of absorption greater than 99%. The packing is employed in industrial systems for heat recovery of flue gases from boilers burning natural gas, which utilize up to 13–15% extra heat and significantly reduce the harmful emissions. The heated and humidified air for combustion in one of the variants creates special conditions for fuel combustion such that the formation of nitrogen oxides is decreased by 3.5 times.


      PubDate: 2016-08-15T02:51:47Z
       
  • Heterogeneous reactive extraction for isopropyl alcohol liquid phase
           synthesis: Microkinetics and equilibria
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Vanessa Walter, Bernhard Pfeuffer, Ulrich Hoffmann, Thomas Turek, Detlef Hoell, Ulrich Kunz
      The reaction kinetics for the liquid phase synthesis of isopropyl alcohol (IPA) from propene (P) and water (W) using a macroporous sulfonic acid ion exchange resin as catalyst were determined experimentally in a multiphase CSTR in the temperature range 398K to 433K at 8MPa. This high pressure is necessary to dissolve propene in the aqueous phase and to ensure a liquid or supercritical state of all components. At typical reaction conditions, the reactants form two immiscible phases; the reaction takes place in the water swollen gel phase of the catalysts microspheres. Due to the large excess of water in the gel phase the compositions in the gel phase, in the macropore fluid, and in the catalyst surrounding aqueous phase are assumed to be identical. For temperatures up to 413K the reaction kinetics for the used catalyst size are not influenced by mass transfer resistances within the catalyst matrix. Two reactions, the formation of IPA and the condensation reaction of two IPA molecules forming the by-product diisopropyl ether (DIPE), are investigated. The experimental results can be described sufficiently by pseudo-homogeneous rate expressions in aqueous phase activities. For the formation of IPA, the forward reaction is first-order in propene and water while the reverse reaction is first-order in IPA. The activation energy of the forward reaction was determined to 115.3kJ/mol. The formation of DIPE is second order with respect to the activity of IPA. The reverse reaction is first order with respect to the activities of DIPE and water. The activation energy was determined to 85.6kJ/mol. Simultaneous chemical and phase equilibria were investigated theoretically using the volume translated Peng-Robinson equation of state (VTPR-EoS) in combination with a g E-mixing rule. Parameters of the used g E-model were adjusted to experimental liquid-liquid equilibrium (LLE) data.


      PubDate: 2016-08-15T02:51:47Z
       
  • Adsorption of mixed DDA/NaOL surfactants at the air/water interface by
           molecular dynamics simulations
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Li Wang, Runqing Liu, Yuehua Hu, Wei Sun
      The adsorption behavior of mixed cationic dodecylamine (DDA)/anionic sodium oleate (NaOL) at different molar ratios at the air/water interface were investigated using molecular dynamics (MD) simulations. Some parameters such as the distribution of headgroups, carbon chains, counterions and water, as well as the headgroups-water radial distribution function, were calculated. The simulation results show that compared to pure DDA and NaOL, their mixtures are more compact and can form a tight monolayer at the air/water interface, indicating higher surface activity. The polar groups of surfactants are tilted into the liquid phase because of strong interactions with water; meanwhile, the hydrophobic carbon chains stretch towards the air phase at a smaller angle than pure surfactant. Water molecules can gather easily and aggregate around the headgroups in the mixed surfactants system. The order of the surface activity is as follows: DDA/NaOL=1/3>DDA/NaOL=1/1> DDA/NaOL=3/1. These results demonstrate a strong synergistic interaction between DDA and NaOL at the air/water interface.
      Graphical abstract image

      PubDate: 2016-08-15T02:51:47Z
       
  • Methodology for evaluating modular production concepts
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Stefan Sievers, Tim Seifert, Gerhard Schembecker, Christian Bramsiepe
      A more flexible and efficient production of chemicals is a requirement for further strengthening the competitiveness in the chemical industry. An approach proposed to achieve this is modular plant design. It offers new opportunities for the supply chain and combines production flexibility and efficiency. However, modular facilities are expected to be built at comparably small scales and loss of economy of scale is a major concern. There is a need to know under which conditions a modular plant design is a beneficial option. Addressing this it would be helpful to have a methodology that includes modeling of production scenarios in a holistic way including supply chain and process simulation and thus allowing a meaningful evaluation. For that reason we developed such a methodology, using the F3 factory concept as an example for modular plant design. Demonstrating the methodology's feasibility an exemplary implementation in a software tool was established enabling comparative simulation and evaluation of batch, continuous and the modular F3 factory production. As unique feature supply chain and process simulation is combined in a single software implementation allowing for statistical analysis to automatically evaluate the economic performance of production concepts under different boundary conditions of the process and the supply chain. The incorporation of those boundary conditions is usually not part of process simulation and goes beyond state of the art approaches. In this paper, the methodology implemented will be presented and the application will be demonstrated using two production scenarios as examples. For the examples investigated, it was found that compared to the conventional production concept the modular F3 factory concept is economically robust concerning the choice of design capacity with regard to diverse market conditions.


      PubDate: 2016-08-15T02:51:47Z
       
  • Synthesis of mesoporous materials SBA-16 with different morphologies and
           their application in dibenzothiophene hydrodesulfurization
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Zhengkai Cao, Peng Du, Aijun Duan, Rong Guo, Zhen Zhao, Hong lei Zhang, Peng Zheng, Chunming Xu, Zhentao Chen
      A series of mesostructured SBA-16 materials with different morphologies were prepared by templating method using triblock copolymer pluronic F127 (EO106PO70EO106) as surfactant and tetraethyl orthosilicate (TEOS) as silicon source. The influences of inorganic salt KCl and the synthesis temperature (temperature of the synthesis process before hydrothermal treatment) from 25 to 55°C on the morphologies of SBA-16 materials were also investigated. The obtained materials were characterized by various techniques, including X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), scanning electron microscope (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption, UV–visible diffuse reflectance spectrum (UV–vis DRS), H2 temperature-programmed reduction (H2-TPR), Raman and X-ray photoelectron spectra (XPS) measurements. The SAXS, SEM and TEM results demonstrated that the SBA-16 materials possessed a body-centred cubic Im3m mesostructure. Five kinds of morphologies were found for the as-prepared SBA-16 materials, while sphere SBA-16 particles were obtained at the synthesis temperatures of 25°C and 30°C; mixed states of decahedral together with sphere were obtained at 38°C; decahedral together with dodecahedral was obtained at 45°C; hexagonal prisms was obtained at 50°C; and tetrakaidecahedron was obtained at 55°C. Moreover, aluminium isopropoxide was incorporated into the SBA-16 materials with a Si/Al molar ratio of 20 through the post-synthesized method, and the corresponding hydrodesulfurization (HDS) activities of NiMo supported catalysts on dibenzothiophene (DBT) were also performed in a micro reactor at T=340°C and P=4MPa with different weight hourly space velocities (WHSV). These NiMo catalysts were denoted as NiMo/S-x. S referred to Al modified SBA-16 supports, and x signified the synthesis temperatures from 25 to 55°C. The synthesis mechanism of SBA-16 exhibiting different morphologies was proposed. Meanwhile, the DBT (500ppm) HDS performance over NiMo/S-50 catalyst exhibited the highest conversion of 95.2% at the WHSV of 20h−1.
      Graphical abstract image

      PubDate: 2016-08-15T02:51:47Z
       
  • Experimental and CFD simulations of fluid flow and temperature
           distribution in a natural circulation driven Passive Moderator Cooling
           System of an advanced nuclear reactor
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Eshita Pal, Mukesh Kumar, Arun K. Nayak, Jyeshtharaj B. Joshi
      The Passive Moderator Cooling System (PMCS) of the Advanced Heavy Water Reactor is designed to remove heat from the moderator passively in case of an extended station black out condition (SBO). The hot heavy-water moderator inside the Calandria rises upward due to buoyancy, cooled in a shell and tube heat exchanger (located within the loop) and returns back to the Calandria, completing a natural circulation loop. The heat exchanger, in turn, is cooled by water from a Gravity Driven Water Pool (GDWP); forming a second loop. This coupled natural circulation loop system provides sufficient cooling to prevent the increase of moderator temperature inside the Calandria vessel beyond safe limits during SBO. The feasibility of such a system should be assessed before it is implemented in the reactor. Thus, a scaled test facility was set up to simulate the thermal hydraulic characteristics of the PMCS. A set of time varying power experiments were performed, which capture the flow initiation from rest phenomena and the multidimensional natural convection flow in a coupled natural circulation system. Next, the experimental geometry was simulated using the three-dimensional computational fluid dynamics code (OpenFoam 2.2.0), which predicted temperature and flow distribution inside the system. The CFD results agree well with the experimental data within ±6%. The flow initiation phenomena shows that the initial flow generated recirculates within the Calandria, after ~900s the flow is able to come out of the Calandria. The experiments show a time lag between the starting of the primary and secondary loop circulation. This work demonstrates the experimental and computational capability to understand and design an effective Passive Moderator Cooling System.


      PubDate: 2016-08-11T04:38:06Z
       
  • CFD-PBM simulation of droplets size distribution in rotor-stator mixing
           devices
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Chengpeng Qin, Chao Chen, Qi Xiao, Ning Yang, Cansheng Yuan, Christian Kunkelmann, Murat Cetinkaya, Kerstin Mülheims
      Rotor-Stator mixing devices (RS) have found widespread application in mixing, dispersion and emulsification processes to acquire the desirable droplet size distribution (DSD) which is critical to the function and quality of products. Thus the precise control of DSD through the rational design and optimization of process or formulation is highly demanded. Computational fluid dynamics (CFD) becomes increasingly important to simulate the complex turbulence flow in RS devices which has significant impact on the final DSD. CFD can also be integrated with population balance equations (PBE) to predict the DSD as long as the droplet breakage and coalescence rates could be accurately modeled by the kernel functions. However, the underlying physics of droplet breakage and coalescence is complex and far from being well understood. We simulated the liquid–liquid two-phase flow and DSD for a weak coalescence emulsification system in a Megatron RS mixer with the CFD-PBM approach, then tentatively proposed a novel approach for correcting the breakage kernels based on the Energy-Minimization Multi-Scale (EMMS) concept. This method features the multi-scale resolution of energy dissipation, and utilizes the so-called meso-scale energy dissipation to derive a correction factor for the breakage rate for PBE. The results show that the new model can greatly improve the CFD-PBM simulation, and the DSD predicted is in good agreement with experiments, demonstrating the rationality and potential of this new approach.


      PubDate: 2016-08-11T04:38:06Z
       
  • Inhibiting effects of transition metal salts on methane hydrate stability
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Traci Y. Sylva, Christopher K. Kinoshita, Stephen M. Masutani
      The behavior of clathrate hydrates in the presence of transition metal salts was investigated using a Differential Scanning Calorimeter (DSC). Specifically, a DSC was employed to determine the onset temperature for methane hydrate decomposition in the presence of ferric chloride hexahydrate, [FeCl2(H2O)4]Cl·2H2O, anhydrous ferric chloride, FeCl3, MnSO4, FeSO4, CuSO4, and AgNO3, and to compare the inhibiting properties of these transition metal salts with NaCl and CaCl2, two well-known salt inhibitors. The degree of methane hydrate inhibition induced by the salts that were studied (as indicated by the reduction in dissociation temperature at a given pressure), when compared between mixtures with the same mole percentages of the salt, increases in the following order: FeSO4≈CuSO4<MnSO4≈AgNO3≈CaCl2<NaCl<FeCl3. A smaller decrease in the dissociation temperature was observed with salts that contained the larger sulfate anion when compared to salts that contained the smaller chloride anion. Smaller decreases in the dissociation temperature were observed with salts that contained smaller cations like Fe2+ when compared to salts that contained larger cations such as Ag+ and Mn2+. It is posited that the interaction between water with salt ions results in hydrate formation inhibition and the strength of the salt ion-dipole bond between the metal ion and water molecules correlates with the degree of inhibition. Consideration of the charge and size characteristics of the anion and cation components of the tested salts appears to explain this behavior.


      PubDate: 2016-08-11T04:38:06Z
       
  • Nucleation curves of methane – propane mixed gas hydrates in
           hydrocarbon oil
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Nobuo Maeda
      The second generation High Pressure Automated Lag Time Apparatus (HP–ALTA MkII) was used to measure the nucleation curves of Structure II (sII)–forming methane–propane mixed gas hydrates on the surface of a quasi–free water droplet suspended in involatile hydrocarbon oil, squalane. The measured nucleation curves were then compared to the previously obtained nucleation curves of the same guest gas hydrate on a quasi–free water droplet supported by perfluorodecalin. The comparison of the two sets of data sets showed that the nucleation rates of the two systems were broadly similar to each other. A simple master nucleation curve was derived for each system as a function of the system subcooling. The model-independent empirical equation that relates the nucleation rate to the system subcooling was J water-guest (s−1 m−2)=2.38×10−39ΔT 26.746 for a quasi-free water droplet suspended in squalane and J water-guest (s−1 m−2)=7.70×10−11ΔT 7.931 for a quasi-free water droplet supported by perfluorodecalin. The nucleation rates predicted by these empirical equations are then compared to the nucleation rates of other relevant systems in the literature. The model-independent analysis method for the derivation of nucleation curves we have developed can be applied to constant cooling ramp data obtained by any experimental techniques.


      PubDate: 2016-08-11T04:38:06Z
       
  • Gas–liquid mass transfer in a falling film microreactor: Effect of
           reactor orientation on liquid-side mass transfer coefficient
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): David Lokhat, Ashveer Krishen Domah, Kuveshan Padayachee, Aman Baboolal, Deresh Ramjugernath
      Microreactors offer a unique platform for chemical syntheses and have been applied to numerous reaction types including nitrations, fluorinations and hydrogenations. A key feature of falling film microreactors is the comparably large specific surface area they afford compared to conventional reactors. The enhanced heat and mass transfer characteristics can be exploited for rapid and exothermic reactions. Adequate understanding of the mass transfer processes occurring within microchannels is necessary for proper reactor design and optimization. In the current study the influence of reaction plate orientation and gas flowrate on liquid-side mass transfer coefficient was investigated via CO2 absorption experiments. Lower plate angles resulted in lower liquid-side mass transfer coefficients. At higher film velocities the rate of mass transfer was greater. The experimentally determined mass transfer coefficients were at least twice as high as those predicted either by film or penetration theory. The enhancement in mass transfer is suggested to be due to cellular convection in the microchannels. For inclined reaction plates, increasing the gas flowrate had a positive effect on the mass transfer characteristics due to induced fluctuations of the gas–liquid interface.
      Graphical abstract image

      PubDate: 2016-08-11T04:38:06Z
       
  • QMOM-based population balance model involving a fractal dimension for the
           flocculation of latex particles
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Mélody Vlieghe, Carole Coufort-Saudejaud, Alain Liné, Christine Frances
      An experimental and computational study of agglomeration and breakage processes for fully destabilized latex particles under turbulent flow conditions in a jar is presented. The particle size distribution (PSD) and the fractal dimension of flocs of latex particles were monitored using an on-line laser diffraction technique. A population balance equation (PBE) was adapted to our problem by including the fractal dimension in its formulation as well as in the aggregation and breakage kernels. The quadrature method of moments was used for the resolution. The adjustment of 4 model parameters was then conducted on the first 6 moments of the PSD for various mean shear rates. The model correctly predicts the evolution of the first 6 moments calculated from the experimental PSD. The experimental results were adequately simulated by a single set of adjusted parameters, proving the relevance of the dependency on the fractal dimension and mean shear rate. A sensitivity analysis was performed on two main adjusted parameters highlighting the major roles of (1) the power to which the mean shear rate is raised in the breakage kernel and (2) the sizes of the colliding aggregates in the collision efficiency model. Finally, analytical relations between the sink and source terms of the breakage or aggregation of the PBE were derived and discussed, highlighting interesting features of the PBE model.


      PubDate: 2016-08-11T04:38:06Z
       
  • Effect of foam processing parameters on bubble nucleation and growth
           dynamics in high-pressure foam injection molding
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Vahid Shaayegan, Guilong Wang, Chul B. Park
      We used an innovative visualization mold to investigate the effect of foam processing parameters on bubble nucleation and growth. This was also done to uncover the mechanisms responsible for cellular structural development in the high-pressure foam injection molding process. The effects of the injection speed, the injection gate geometry, the blowing agent content, the melt flow rate and the use of talc as a heterogeneous nucleating agent on the formation and dynamics of cell bubbles were all explored. In the high-pressure foam injection molding process with a proper packing pressure, the overall cell density did not change with the injection speed nor with the injection gate resistance. However, the cell density increased significantly with the blowing agent's concentration and with a nucleating agent. We also observed the growth mechanism of the bubbles in a confined mold cavity, and concluded that the bubble growth rate decreased as the cell density increased. In addition, the satelliting phenomenon, i.e. bubble nucleation around the previously nucleated cells, was observed. This was due to the induced stress fluctuations in the surrounding melt, which could eventually affect the final cellular structure.


      PubDate: 2016-08-11T04:38:06Z
       
  • Mass transfer, gas hold-up and cell cultivation studies in a bottom
           agitated draft tube reactor and multiple impeller Rushton turbine
           configuration
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Petri Tervasmäki, Marko Latva-Kokko, Sanna Taskila, Juha Tanskanen
      Gas–liquid mass transfer is an important phenomenon in aerobic microbial cultivations, and the mass transfer performance of an industrial reactor strongly affects the overall process economics. Traditionally, industrial and laboratory bioreactors have been agitated with flat disc turbines (Rushton turbines) although there are many variants to this design. In addition, pneumatically agitated reactors such as bubble columns and airlift reactors have been studied and used by the industry. In this study we utilize an agitated draft tube reactor in cell cultivation and mass transfer studies. A standard reactor geometry agitated with three Rushton turbines was compared to Outotec OKTOP®9000 reactor which is a draft tube reactor agitated with a single impeller located just below the draft tube. The experiments included cell cultivation with Pichia pastoris yeast, determination of overall mass transfer coefficient by dynamic gassing in method and measurement of local gas hold-up by electrical impedance tomography (EIT). In addition, agitation power was estimated from the power consumption of the DC-motor. OKTOP®9000 reactor was found to have higher k L a values than the STR with similar agitation power and gas flowrate. The overall gas hold-up was similar in both geometries at same power inputs and gas flow rates. However, some significant differences were detected in the distribution of gas phase between the two geometries especially in the axial direction. Also changes in the gas dispersion regime can be detected from the spatial distribution of the gas hold-up measured by EIT. The cell cultivation experiments showed the applicability of this type of agitated draft tube reactor to bioprocesses although a direct comparison with Rushton geometry is not straightforward.
      Graphical abstract image

      PubDate: 2016-08-11T04:38:06Z
       
  • Stability analysis of stratified
           Rayleigh–Bénard–Poiseuille convection. Part II: Influence
           of thermocapillary forces
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Éliton Fontana, Erasmo Mancusi, Antônio A.U. de Souza, Selene M.A.G.U. de Souza
      The development of convective cells in horizontal stratified systems can be induced by buoyancy or thermocapillary forces (Marangoni effect). When both mechanisms of instability are present it is expected a non-trivial influence of one over the other, with the main characteristics based primarily on the ratio between the buoyancy forces acting in each layer. In this study, linear stability analysis is used to investigate the influence of the thermocapillary effect in double layer stratified systems confined between two solid walls and heated from below, including cases where a pressure gradient induces fluid flow parallel to the walls. To simplify the analysis, it is assumed that the fluids in both layers have similar properties and the interface deformation is neglected. The presence of thermocapillary forces acting on the interface generates a complex behavior, particularly when the upper layer is deeper than the lower layer, which causes the convective cells to emerge initially in the upper layer. In this case, oscillatory states can appear as a result of the competition between the mechanisms of instability. This behavior is not observed if the thermocapillary forces are neglected; therefore, in order to obtain a complete picture of the system stability, it is important to include the Marangoni effect. The increases in the Reynolds and Prandtl numbers showed a similar effect. For low Re or Pr values, the thermocapillary forces initially stabilize the system, however, after a certain threshold the increase in the Marangoni number tends to destabilize the system. The presence of parallel flow also hinders the formation of oscillatory states. When the convective cells emerge initially on the lower layer, the increase in the Marangoni number facilitates the development of the cells, since the thermocapillary forces always act in the same direction as the buoyancy forces at the interface.


      PubDate: 2016-08-11T04:38:06Z
       
  • Experimental study of the formation and deposition of gas hydrates in
           non-emulsifying oil and condensate systems
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Erlend O. Straume, Celina Kakitani, Daniel Merino-Garcia, Rigoberto E.M. Morales, Amadeu K. Sum
      Potential flow assurance problems in oil and gas pipelines related to gas hydrates have traditionally been resolved by implementing avoidance strategies, such as water removal, insulation, and injection of thermodynamic inhibitors. As a means of lowering development and operational costs in the industry, hydrate management is becoming a more viable approach, a strategy which seeks to minimize the risk of plugging conditions using methods that allow transportability of hydrate slurries with the hydrocarbon production fluids. A thorough understanding of how hydrates form and behave in different multiphase systems is essential for safe implementation of various hydrate management methods. In order to increase insight into the different processes leading to hydrate plug conditions, a number of experiments have been performed using a visual rocking cell to measure and observe the various stages of hydrate formation, deposition and accumulation during continuous mixing and motion induced by the oscillation of the rocking cell. The fluid combinations studied in these experiments considered oil+water+gas and condensate+water+gas. The effects of added monoethylene glycol (MEG) and a model anti-agglomerant (AA) were also studied in some of the experiments. The experiments showed that hydrate deposition is prevalent in all systems studies, but it was observed that there was a higher tendency to deposit on surfaces exposed to condensate or the gas phase than on oil wetted surfaces. Hydrate growth, agglomeration and bedding were observed in the experiments. Highly porous hydrate deposits formed in conditions with a large temperature gradient between the bulk and the surface, and high subcooling conditions, then suffering from sloughing due to the shear of the fluids on the deposit. Hydrate formation in an experiment with mineral oil, 30% water cut and anti-agglomerant resulted in transportable hydrate slurry. Both the condensate and mineral oil tested were non-emulsifying, but shear-stabilized dispersion of the liquid phases was created prior to hydrate formation by mixing induced by the motion of the cell. Interestingly, the dispersion appeared to completely phase-separate, momentarily, upon hydrate formation onset.


      PubDate: 2016-08-11T04:38:06Z
       
  • A mathematical model for carbon fixation and nutrient removal by an algal
           photobioreactor
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Ahmed M.D. Al Ketife, Simon Judd, Hussein Znad
      A comprehensive mathematical modeling method for Chlorella vulgaris (Cv) has been developed to assess the influence of nutrient concentration (total nitrogen TN= 28–207 and total phosphorus TP= 6–8mgL−1) and irradiation intensity (I = 100–250 μE) at feed gas CO2 concentrations (C c,g ) of 0.04-5%. The model encompasses gas-to-liquid mass transfer, algal uptake of carbon dioxide (C d ), nutrient removal efficiency (RE for TN and TP), and the growth biokinetics of Cv with reference to the specific growth rate µ in d−1. The model was validated using experimental data on the Cv species growth in an externally illuminated photobioreactor (PBR). The fitted parameters of the model were found to be in good agreement with experimental data obtained over the range of cultivation conditions explored. The mathematical model accurately reproduced the dynamic profiles of the algal biomass and nutrient (TN and TP) concentrations, and light attenuation at different input C c,g values. The proposed model may therefore be used for predicting algal growth and nutrient RE for this algal species, permitting both process optimization and scale-up.


      PubDate: 2016-08-07T04:36:19Z
       
  • Computational minimization of the specific energy demand of large-scale
           aerobic fermentation processes based on small-scale data
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Dirk Kreyenschulte, Frank Emde, Lars Regestein, Jochen Büchs
      During the assessment of the potential profitability and feasibility of new production routes, aerobic fermentation can turn out to be a major factor contributing to the operating expenditure of the overall process. The accurate evaluation of its energy demand is, therefore, of prime importance. To this end, a tool was developed based on established and generally accepted correlations considering relevant parameters and constraints for bioreactor operation. While the assessment is performed for large-scale reactors (10–100m3), it is based on data from small-scale experiments using the oxygen transfer rate as a scale-up criterion. Among the evaluated constraints, the flooding-loading transition of the bioreactor proved to be a crucial criterion for culture volumes of more than 20m3. Minimum energy demand for cooling, agitation, and aeration could thus be achieved at low agitation and high aeration intensity. At moderate oxygen transfer requirements, bioreactor pressurization was not found to increase energy efficiency of aerobic processes. It was, however, shown to be indispensable for processes with high oxygen demands and elevated foam formation. The tool was applied to assess itaconic acid as well as lysine fermentation processes. Due to considerable differences in oxygen demand, average power consumption was found to be at 0.51kWm−3 (itaconic acid) and 2.61kWm−3 (lysine), thus arguing against the utilization of general rule of thumb values. The established tool, therefore, provides an efficient means to specify estimates of the energy demand in consideration of the respective process.


      PubDate: 2016-08-07T04:36:19Z
       
  • Direct synthesis of hierarchical USY zeolite for retardation of catalyst
           deactivation
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Baoyu Liu, Kaihong Xie, Su Cheun Oh, Dalei Sun, Yanxiong Fang, Hongxia Xi
      Hierarchically structured zeolite Y was hydrothermally synthesized using a water glass containing organosilane surfactant as a mesoscale template. The resulting hierarchical zeolite Y was characterized by a complementary combination of X-ray powder diffraction, Fourier transform infrared spectroscopy, N2 adsorption–desorption isotherms, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, 27Al MAS NMR spectroscopy and density functional theory (DFT) calculation. These results indicated that the hierarchical zeolite Y contained disordered intracrystal mesopores. In addition, quantum chemical calculation results showed that organosilane surfactants could be easily dispersed into the viscous gel used in the synthesis of zeolite Y, inhibiting the phase-separation phenomenon. Hierarchical zeolite Y exhibited remarkably higher resistance to deactivation in the aldol condensation reaction of benzaldehyde with n-butyl alcohol than that of commercial zeolite Y, which is attributed to the highly mesoporous structure that can improve access of reactant molecules to the active sites and minimize the diffusion length of coke precursors out of the zeolite matrix. Such hierarchically porous zeolite Y is very attractive for applications in adsorption and catalysis involving bulky molecules.


      PubDate: 2016-08-07T04:36:19Z
       
  • Cellulose acetate nanofiber electrospun on nylon substrate as novel
           composite matrix for efficient, heat-resistant, air filters
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): A. Nicosia, T. Keppler, F.A. Müller, B. Vazquez, F. Ravegnani, P. Monticelli, F. Belosi
      Cellulose acetate (CA) nanofibers were prepared via electrospinning to obtain a high quality factor (QF) fibrous mat for aerosol particle filtration. To this purpose, special attention was paid to the substrate material used to collect the nanofibers. Different materials (glassine paper, Lyocell, nylon grids) were investigated for use as substrates in the membrane spinning process. Membrane and membrane fiber morphologies were characterized by optical microscope and scanning electron microscope (SEM) analyses. Results show that the arrangement of the membrane fibers is directly correlated to the morphology of the collecting substrate material. Experiments shows that the electrospun nanofiber web tends to recreate the specific character of the supporting textile texture. A support with a pronounced bi-dimensional structure should be preferred. A regular grid, made of nylon, is selected for the composition with CA nanofibres. By maintaining the same support, various electrospinning parameters such as the spinning solution CA concentration (14wt%, 18wt%) and spinning volume (15–120μL) of the membranes are tested in terms of air filtration performance. Filtration tests are performed by measuring the filter penetration against neutralized aerosol particles. Basis weight, solid volume fraction and thickness parameter were investigated to find the best arrangement. The filtration efficiency of stacked layers is analyzed at variable thickness of the building block element. An electrospun membrane of above 60μm thickness, combined with the selected substrate, increases the QF and improve its reproducibility. The QF can be further increased with an optimized porosity of the nylon substrate. The best QF of 0.080±0.050Pa−1 at 300nm was obtained by spinning a 14wt% CA solution in an acetone- DMSO-acetic acid solvent mixture on a nylon grid with 100μm mesh size producing fleeces with a very low pressure drop (7Pa). Thermogravimetric analyses (TGA) and SEM imaging demonstrated the stability of the composite filter morphology up to 200°C.


      PubDate: 2016-08-07T04:36:19Z
       
  • Voronoi analysis of the packings of non-spherical particles
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Kejun Dong, Chuncheng Wang, Aibing Yu
      We present a structural analysis of the packings of identical non-spherical particles based on Voronoi cells. The packings are generated by discrete element method (DEM) simulations. The particles include axisymmetric ellipsoidal particles from oblates to prolates and cylindrical particles from disks to rods. The Voronoi cells are constructed by virtue of space discretization and surface reconstruction, which is shown to be universal for different shapes. The effects of particle aspect ratio and sliding friction coefficient on the properties of Voronoi cells, including the reduced volume, reduced surface area and sphericity, are quantified. The reduced volume and surface area are found to observe log-normal distributions, while their mean values and standard deviations have different dependencies on particle shape and friction. By analyzing the correlations and using inherent relationships between different Voronoi cell properties, we establish a group of universal equations to predict these distributions according to particle sphericity and overall packing fraction. Such findings can not only improve our understanding on the packings of non-spherical particles but also provide a basis for evaluating the transport properties and advancing the statistical mechanics theory for granular matter composed of non-spherical particles.
      Graphical abstract image

      PubDate: 2016-08-07T04:36:19Z
       
  • On an efficient hybrid soft and hard sphere collision integration scheme
           for DEM
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): K.A. Buist, L.J.H. Seelen, N.G. Deen, J.T. Padding, J.A.M. Kuipers
      This paper introduces a novel hybrid collision integration scheme that combines the benefits of the hard-sphere and the soft-sphere methodology. It assumes that the larger part of the collisions are binary and can be solved in one step. The remainder of the collisions involving more than two particles are handled with a classical soft-sphere scheme. Results for a bounding box problem, employing the classical soft-sphere scheme and the hybrid scheme are compared in terms of energy budget conservation. The hybrid scheme is more accurate and more importantly it is roughly one order of magnitude faster.


      PubDate: 2016-08-07T04:36:19Z
       
  • Reduction kinetics of lanthanum ferrite perovskite for the production of
           synthesis gas by chemical-looping methane reforming
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Xiaoping Dai, Jie Cheng, Zhanzhao Li, Mengzhao Liu, Yangde Ma, Xin Zhang
      The reduction kinetics of LaFeO3 oxygen carrier for the production of synthesis gas by chemical-looping methane reforming (CLMR) is investigated in the present work. The stoichiometric relationship between oxygen carrier and methane in chemical-looping process is established by temperature programmed surface reaction (TPSR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) characterization. The effects of reduction conditions, namely, gas to solid molar ratio, temperature and sequential redox reaction on the oxygen carrier conversion are investigated. The results from Hancock and Sharp method suggest that the phase boundary control is likely to be dominant. The power law model (PLM), shrinking core model (SCM), as well as nucleation and nuclei growth model (NNGM) are considered to interpret the reduction kinetics of LaFeO3 with methane to synthesis gas. The obtained results show that the 2-D NNGM best describes the experimental data providing parameters with adequate statistical fitting indicators. The model validity is also verified by the data from continuous flow reaction and sequential redox cycles to simulate chemical-looping methane reforming process. The apparent activation energy is estimated and compared with values from the literature data.
      Graphical abstract image

      PubDate: 2016-08-07T04:36:19Z
       
  • Kinetic study of vapor-phase Beckmann rearrangement of cyclohexanone oxime
           over silicalite-1
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Chao Ge, Zhikai Li, Gang Chen, Zhangfeng Qin, Xiaofeng Li, Tao Dou, Mei Dong, Jiangang Chen, Jianguo Wang, Weibin Fan
      The intrinsic kinetics for vapor-phase Beckmann rearrangement of cyclohexanone oxime (CHO) to caprolactam (CPL) over fresh silicalite-1 was studied at atmospheric pressure by an improved approach that combines the differential and the integral methods. To keep the reaction zone temperature constant at high flow rate and obtain homogeneous mixture of CHO and methanol largely different in boiling point, a special fixed-bed tubular reactor was designed. The relationship of deactivation rate with weight hourly space velocity (WHSV) was investigated in a wide range of CHO concentrations under high gas superficial velocity. The rate equation was directly deduced by the differential method on the basis of the dependence of CHO disappearance rate on CHO and CPL partial pressures. The reaction mechanism and rate-limiting step were determined by in situ infrared spectroscopy and comparison of the catalytic results of fresh and partially poisoned silicalite-1. The kinetic parameters were estimated and statistically tested by the integral method. It is shown that the vapor-phase Beckmann rearrangement of CHO to CPL occurs via a single-site surface reaction route with activation energy of 94.69kJ/mol, and desorption of CPL is the rate-limiting step.


      PubDate: 2016-08-07T04:36:19Z
       
  • A liquid distribution model for a column with structured packing under
           offshore conditions
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Yongho Son, Kwangjoon Min, Kwang Soon Lee
      A liquid distribution model for a packed column with structured packing under offshore conditions is proposed. In this paper, permanent tilt and dynamic roll motion were selected as representative offshore conditions for the proposed model, considered to be the most severe offshore conditions. The proposed model is composed of an intersection network model with a liquid split algorithm. Parameter estimation was performed for the proposed model using published experimental data to adjust the parameters in the liquid split algorithm for the considered offshore conditions. A comparison between the liquid distribution of the proposed model and that of literature data was also presented. Using the adjusted parameters and proposed model, the main characteristics of liquid distribution under offshore conditions were investigated. In addition, the effects of column diameter and packed height on liquid distribution were studied. The results obtained from the proposed model could be the basis for the design of an absorption column installed on a buoyant platform like a floating production storage and offloading (FPSO) unit.


      PubDate: 2016-08-07T04:36:19Z
       
  • Thermodynamic and mass transfer modeling of carbon dioxide absorption into
           aqueous 2-piperidineethanol
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Brent J. Sherman, Arlinda F. Ciftja, Gary T. Rochelle
      Amine scrubbing is a necessary technology to offset CO2 emissions from fossil-fuel power plants. Of the many solvents studied, hindered amines are of particular interest for their marriage of the capacity of tertiary amines with rates a hundredfold greater than tertiary amines. The relatively rapid rates of hindered amines have not been adequately explained, despite their extensive use in commercial solvents. This work seeks to explain the rapid rate of mass transfer of 2-piperidineethanol (2PE) and uses this rationale to draw general conclusions on hindered amines. Quantitative 13C NMR data were collected to determine the equilibrium of carbamate in 30wt% 2PE. Using these data along with VLE and pK a data, a rigorous thermodynamic model of 8 molal 2PE was built with electrolyte-NRTL and activity-based kinetics. Wetted-wall column flux data were fit to create the activity-based mass transfer model. Using this comprehensive model, the mass transfer rate was examined through sensitivity studies and Brønsted correlations. This work shows that 2PE forms a more stable carbamate than 2-amino-2-methyl-1-propanol. The carbamate reaction is the most significant component of mass transfer at 40°C. The Brønsted correlation for carbamate reactions of unhindered amines predicts the rate of carbamate reaction of 2PE, but the Brønsted correlation for bicarbonate underpredicts the regressed rate. The CO2 solubility is fit with five parameters with an ARD of 0.84%. The kinetics are fit with a carbamate- and a bicarbonate-forming reaction with an ARD of 7.03%. The chief conclusions are (1) that the rapid mass transfer of hindered amines is due to the formation of carbamate and the high pK a of the amine, (2) the carbamate formation rate appears unimpeded by steric hindrance and is predicted by a Brønsted correlation, suggesting that hindered amines react in the same manner as unhindered amines.
      Graphical abstract image

      PubDate: 2016-08-07T04:36:19Z
       
  • Modelling of a Simulated Moving Bed in case of non-ideal hydrodynamics
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): L. Fangueiro Gomes, F. Augier, D. Leinekugel-le-Cocq, I. Vinkovic, S. Simoëns
      The one-dimensional hydrodynamic model proposed by Gomes et al. (2015) is coupled with adsorption and validated by comparing the concentration profiles of the one-dimensional model with those given by the CFD model of one adsorption column including obstacles as distribution network and beams. This one-dimensional model is capable of predicting the CFD results for different mass transfer rates, while the traditional dispersed plug flow (DPF) model is relevant for slow mass transfer rates only. The model proposed by Gomes et al. (2015) is capable of reproducing the adsorber Residence Time Distribution (RTD) while dissociating the selective zones from the non-selective ones. It is based on the CFD techniques developed by Liu and Tilton (2010) and Liu (2012) that transport the moments of the fluid age distribution and consequently calculate the degree of mixing (Danckwerts, 1958; Zwietering, 1959). Then, this new model is integrated in a cyclic solver in order to perform Simulated Moving Bed (SMB) studies. The new model provides a detailed hydrodynamic description, which appears to be mandatory especially when mass transfer exchanges are fast, without undergoing the prohibitive simulation times of CFD models.


      PubDate: 2016-08-03T04:32:19Z
       
  • Colloid particle transport in a microcapillary: NMR study of particle and
           suspending fluid dynamics
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Einar O. Fridjonsson, Joseph D. Seymour
      Precise manipulation of the hydrodynamic interaction between particles is particularly important for operation of microfluidic devices. Shear-induced migration gives rise to dynamical patterns within the flow that have been observed in a range of systems. In this work NMR ‘active’ colloidal particles (a=1.25µm) at volume fraction of 22% in an aqueous phase are flowed through a µ-capillary (R=126µm) and the transport dynamics of the particle and suspending fluid phases are studied using dynamic NMR techniques. Simultaneous interrogation of shear rheology of the suspending fluid and particle phases of colloidal suspensions is presented. The dynamic behavior of the suspending fluid is shown to carry within it information about the structure of the colloidal particle ensembles on the time scales investigated (Δ=25ms→250ms) providing rich experimental data for further investigation and model verification. The importance of determining the particle concentration profile within μ-capillaries is explicitly demonstrated as shear induced migration causes significant concentration gradients to occur at strong flow conditions (i.e. Pe p =270).


      PubDate: 2016-08-03T04:32:19Z
       
  • Analogy of absorption and distillation processes. Wetted-wall column study
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): F.J. Rejl, J. Haidl, L. Valenz, T. Moucha, M. Schultes
      This article is the second one from a pair focusing on the mass transfer fundaments and the analogy between the processes of absorption and distillation. The wetted wall column, a device with known interfacial area, was built for this purpose enabling evaluation of the mass-transfer coefficients instead of the volumetric mass-transfer coefficients usually provided by experiments in the packed columns. The analogy of the processes has been assessed by comparison of the mass-transfer characteristics (HETP, individual mass-transfer coefficients k L and k G) evaluated on the basis of the absorption experiments with those found under the distillation conditions. In the prior paper the results of the absorption experiments performed under distillation-like conditions have been published in the form of dimensionless correlations S h L = 0.33 Re L − 0.12 S c L 0.47   a n d   S h G = 0.012 R e LG 0.90 S c G 0.61 . In this paper we present results of the distillation experiments in the form of the HETP data and mass-transfer coefficients evaluated by the profile method. The experimental data are compared with those predicted on the basis of the absorption experiments results. The experimental HETP data acquired on the methanol-n-propanol and ethanol-n-propanol systems agree within 10–20% with the data predicted. The distillation mass-transfer coefficients evaluated by the profile method were correlated in the dimensionless form S h L = 0.25 Re L − 0.12 S c L 0.47   a n d   S h G = 2.3 ⋅ 10 − 3 R e LG 1.07 S c G 0.61 . The distillation k L values have been found to be 24% lower and the k G values 13% lower than the ones predicted according to absorption correlations. The gas-phase mass-transfer coefficient, k G, exhibits higher dependence on the vapor velocity than it was found in standard absorption measurements. Similar difference was found also for packed columns in previous works. Apparently, there is at least one unaccounted phenomenon which affects differently the mass-transfer performance of absorption and distillation packed columns. Poor results of the present diffusion models have been noticed in this work preventing deeper study of these differences. Improvement of these models is found to be inevitable for the further research in this area as well as for the reliable rate-based modeling of the industrial absorption and distillation columns.


      PubDate: 2016-08-03T04:32:19Z
       
  • A comprehensive numerical investigation on the hydrodynamics and erosion
           characteristics in a pressurized fluidized bed with dense immersed tube
           bundles
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Chenshu Hu, Kun Luo, Shiliang Yang, Shuai Wang, Jianren Fan
      Based on the coupling method of computational fluid dynamics (CFD) with discrete element method (DEM), numerical investigation on the gas-solid hydrodynamics and erosion characteristics is conducted in a 3-D pressurized fluidized bed with immersed tube bundles. The effects of operating pressure on time-averaged solid-phase characteristics, solid circulation features, granular temperature and tube erosion patterns are analyzed. Elevated pressure accelerates both upward and downward particle flows, resulting in a lower solid concentration in the bottom part compared to the upper part. A theory is proposed to explain the occurrence of large solid velocity fluctuation. The distinct erosion distribution of each tube is found to be strongly related to solid flux distribution. The mechanism of bubble-induced tube erosion is represented and validated by simulation result.


      PubDate: 2016-07-28T09:05:01Z
       
  • A novel robust regression model based on functional link least square
           (FLLS) and its application to modeling complex chemical processes
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Yan-Lin He, Qun-Xiong Zhu
      In this paper, a novel robust regression model is proposed. The proposed robust regression model is called functional link least square (FLLS). The idea of the proposed FLLS model arises from the functional link artificial neural network (FLANN). The FLANN model can be established by using the Error Back-propagation algorithm. However, the performance of the FLANN model is limited. Different from the FLANN model, the proposed FLLS model can achieve an optimal regression model by using the least square algorithm. The proposed FLLS model has some salient features: first, the algorithm of FLLS is extremely fast; secondly, the training errors of the FLLS model can be nearly minimized to be zero; third, the testing performance of FLLS model is robust. In order to evaluate the performance of the proposed regression model, case studies of modeling two complex chemical processes are provided. Two more models of the FLANN and the partial least square (PLSR) are also developed for comparisons. Results illustrated that the proposed FLLS regression model could significantly improve the testing performance.


      PubDate: 2016-07-28T09:05:01Z
       
  • Microparticle trajectories in a high-throughput channel for contact-free
           fractionation by dielectrophoresis
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Yan Wang, Fei Du, Georg R. Pesch, Jan Köser, Michael Baune, Jorg Thöming
      Continuous, contact-free fractionation of sensitive microparticles at high throughput is a challenge. For this purpose, we developed a sheath flow assisted dielectrophoretic (DEP) field-flow separator with a tailored arrangement of cylindrical interdigitated electrodes (cIDE) and observed size-dependent trajectories of dispersed particles. Using a voltage input of 200Veff at a frequency of 200kHz, polystyrene particles (45, 25, and 11µm in diameter) levitated to different heights along the channel length due to a negative DEP force. Experimental observations agree well with simulated particle trajectories that were obtained by a modified Lagrangian particle tracking model in combination with Laplace's and Navier–Stokes equations. By exploiting the size-dependent levitation height difference the desired particle size fraction can be collected at a specific channel length. The required channel length of the proposed cIDE separator increases with decreasing particle size to be separated. The quality of theoretical fractionation, which we quantify by resolution, improves strongly with reduced collector width, reduced volume flow rate and increased voltage input. The sensitivity of these dependencies increases with decreasing particle size. We calculated a theoretical throughput of up to 47mLmin−1 when trading-off design and operation parameters, allowing for contact-free fractionation of sensitive microparticles with negligible shear stress.


      PubDate: 2016-07-24T10:46:20Z
       
  • Structural characteristics of adlayer in heterogeneous catalysis
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Fei Sun, Wen Lai Huang, Jinghai Li
      This paper explores the adsorbate distributions in the adlayer for a model system of heterogeneous catalysis, A+B→AB. Relevant kinetic mechanisms are revealed in terms of Shannon entropy via kinetic Monte Carlo (KMC) simulations. It is reckoned that reactions account for the clustering of the adsorbates, whereas diffusion and desorption tend to homogenize the adsorbate distribution besides adsorption, and diffusion exhibits a relatively stronger role. The clustering tendency seems to compete with the homogenizing one, showing alternate dominance in microscale space and time. The compromise between these two tendencies was reflected as the extremal tendencies at the mesoscale and the macroscale. However, such extremal tendencies can be maximization or minimization of Shannon entropy, depending on the choice of the initial state, implying the insufficiency of a single extremal function of Shannon entropy.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
       
  • Modelling agglomeration and deposition of gas hydrates in industrial
           pipelines with combined CFD-PBM technique
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Boris V. Balakin, Simon Lo, Pawel Kosinski, Alex C. Hoffmann
      Hydrates of light hydrocarbons are frequently formed during the subsea petroleum production. These crystalline ice-like solids may accumulate at concentrations sensitive from the flow assurance point of view, increasing the overall pumping costs and imposing sufficient risk of the pipe blockage. Modern trend in the assessment of hydrate-related risks is the development of numerical models of multiphase flows laden by hydrates. The present paper describes a computational fluid dynamic (CFD) model capable to simulate turbulent slurry of oil, water and gas hydrates. The population balance technique (PBM) coupled with CFD enables to predict such details of the process as the formation of hydrate phase, agglomeration of formed solids and granular interactions within the hydrate phase. The simulation results, validated with experimental data in terms of the slurry rheology, highlight flow patterns for a pipe system typical in oil industry. The model is in addition compared to the hydrate kinetics model from Colorado School of Mines (CSMHyK).


      PubDate: 2016-07-24T10:46:20Z
       
  • CFD optimization of feedstock injection angle in a FCC riser
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Sheng Chen, Yiping Fan, Zihan Yan, Wei Wang, Xinhua Liu, Chunxi Lu
      Feedstock injection zone is a key section for fluid catalytic cracking (FCC) riser reactor. In conventional design of commercial FCC risers, the injection angle of the feedstock is 30° upward with the riser axis, which is found to easily cause nonuniform oil-catalyst contact and severe back-mixing in the feedstock injection zone. In this work, the effect of feedstock injection angle is investigated by performing 3-D simulations with seven injection configurations including three inclined upward, one horizontally and three inclined downward. The two-fluid model (TFM) and the energy-minimization multi-scale (EMMS) drag is combined in simulations. Comparison with experimental data is conducted in terms of the profiles of solids and feed volume fractions. Several variables including the backflow ratio, the radial nonuniformity index and the mean residence time of feed, are further introduced to quantify the hydrodynamic dependence of flow and mixing on the injection settings. It is found that the downward injection schemes are better to realize uniform mixing and matching between catalysts and feed than the upward injection schemes. A 30° downward injection angle is desired to improve the distributions of catalysts and feed, reduce the catalyst-feed contacting time and eliminate the effect of secondary flow on severe back-mixing near the riser wall.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
       
  • Multi-objective operation optimization of ethylene cracking furnace based
           on AMOPSO algorithm
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Zhiqiang Geng, Zun Wang, Qunxiong Zhu, Yongming Han
      The objective of this article is to research and design a multi-objective operation optimization strategy and comprehensive evaluation method of solutions, to efficiently solve the multi-objective operation optimization problem of ethylene cracking furnace. An adaptive multi-objective particle swarm optimization (AMOPSO) algorithm is proposed and developed based on dynamic analytic hierarchy process (AHP). The algorithm adopts fuzzy consistent matrix to select the global best solution, which ensures the right direction of particle evolution. Furthermore, the evolution state is measured to adjust the weight and learning coefficients adaptively. The proposed method is applied to the operation optimization of ethylene cracking furnace. Two cases are studied including the fixed cracking cycle with four objectives and the non-fixed cracking cycle with five objectives. According to the preferences, decision makers can select the appropriate operation optimization conditions from alternative Pareto optimal solutions by the results of fuzzy evaluation. A feasible solution is provided for the multi-objective operation optimization of ethylene cracking furnace.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
       
  • Influence of the heating method on the particle characteristics of copper
           oxide powders synthesized from copper nitrate aqueous solutions
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Tomoomi Segawa, Tomonori Fukasawa, An-Ni Huang, Yoshikazu Yamada, Masahiro Suzuki, Kunihiro Fukui
      The influence of the heating method and rate on the morphology of CuO powders synthesized from Cu(NO3)2·3H2O aqueous solutions by denitration was investigated. The median diameter of the obtained powder was found to decrease as the heating rate increased, independent of the heating method. The microwave heating (MW) method remarkably reduced the particle size and enhanced the irregularity and disorder of the shape and surface of the particles, which were found to be more widely distributed. In contrast, the microwave hybrid heating (MHH) method (i.e., a combined usage of microwave and external heating) yielded the most spherical particles with the smoothest surface. It was also found that this heating method sharpened the particle size distribution and had higher energy efficiency than the MW method. Numerical simulations also indicated a difference in the energy efficiency between these two methods. The simulations also revealed that the MHH method could heat the whole reactor more uniformly with a lower microwave output. Moreover, the morphological difference of the powders obtained by these heating methods can be potentially explained by the difference in the simulated bulk temperature distribution and the intensity of the formed hot spot in the CuO particles caused by microwave irradiation.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
       
  • Three-dimensional simulation of micrometer-sized droplet impact and
           penetration into the powder bed
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Hua Tan
      In recent years, various drop-on-demand inkjet technologies capable of precisely delivering micron-sized droplets have been adopted in a few novel powder-based 3D printing processes. The droplet-powder interaction is an important step in these 3D printing technologies. In this paper, we propose a direct numerical simulation method to study the micron-sized droplets impacting on the powder bed. Since the powder particle size in our study is comparable to that of impacting droplets, the powder bed is modeled with a large number of rigid solid spheres fixed in their positions during the droplet impact. A set of important dimensionless parameters and scaling arguments is presented to elucidate the underlying physics involved in the micron-sized droplets impacting on powder. The Cartesian grid based volume-of-fluid method is used to track the immiscible liquid and air interface during the droplet-powder interaction. A contact angle model is proposed to include the wetting effect of the liquid agent on powder particles. The proposed numerical methods are implemented in an open-source code Gerris. Two numerical tests relevant to our study are conducted to validate the modified simulation code. Finally, we carry out simulations of a micrometer-sized droplet impacting on the powder bed with three different impact velocities. For low impact velocity, the droplet can even gain the momentum in the early stage due to strong capillary forces at contact lines compared to inertial force. The large impact velocity results in a wider spread and deeper penetration, however the liquid distribution inside the powder bed can be segmented because of high impact energy. The numerical method proposed in our study can be used to design suitable droplet-powder systems as well as determine optimal printing conditions in the inkjet-assisted powder-based 3D printing technologies.


      PubDate: 2016-07-24T10:46:20Z
       
  • On fiber behavior in turbulent vertical channel flow
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Niranjan Reddy Challabotla, Lihao Zhao, Helge I. Andersson
      In the present work, the dynamic behavior of inertial fibers suspended in a turbulent vertical channel flow has been investigated. The three-dimensional turbulent flow field was obtained from the Navier–Stokes equations by means of direct numerical simulation in an Eulerian reference frame. The fibers were modeled as prolate spheroidal particles in a Lagrangian frame and characterized by their inertia and shape. The translation and rotation of the individual fibers were governed by viscous forces and torques as well as by gravity and buoyancy according to Newton’s laws of motion. The test matrix comprised four different Stokes numbers (inertia) and three different aspect ratios (shape). The twelve different fiber types were suspended both in a downward and in an upward channel flow. Fiber orientation and velocity statistics were compared with channel flow results in absence of gravity. The results showed that gravity has a negligible effect for fibers with modest inertia, i.e. low Stokes numbers, whereas gravity turned out to have a major impact on the dynamics of highly inertial fibers. Irrespective of the bulk flow direction, a preferential alignment of the inertial fibers with the gravity force was found in the channel center where fibers have been known to orient randomly in absence of gravity. In the downward channel flow, the drift velocity of the fibers towards the walls was substantially higher for fibers than for spheres and also higher than when gravity was neglected. In the upward flow configuration, the modest drift velocity of inertial spheres was totally quenched for all fibers irrespective of shape. The suppressed drift velocity resulted in a more uniform fiber distribution throughout the channel as compared to the distinct near-wall accumulation in downward flow and in absence of gravity. This suggests that an upward flow configuration should be the preferred choice if a uniform fiber distribution is desired, as in a biomass combustion reactor.


      PubDate: 2016-07-24T10:46:20Z
       
  • CuO-Fe2O3-CeO2/HZSM-5 bifunctional catalyst hydrogenated CO2 for enhanced
           dimethyl ether synthesis
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Xinhui Zhou, Tongming Su, Yuexiu Jiang, Zuzeng Qin, Hongbing Ji, Zhanhu Guo
      A series of CuO-Fe2O3-CeO2 catalysts with various CeO2 doping were prepared via the homogeneous precipitation method, characterized and mechanically mixed with HZSM-5. Their feasibility and performance for the synthesis of dimethyl ether (DME) via CO2 hydrogenation in a one-step process were evaluated. The formed stable solid solution after the CuO-Fe2O3 catalyst modified with CeO2 promoted the CuO dispersion, reduced the CuO crystallite size, decreased the reduction temperature of highly dispersed CuO, modified the specific surface area of the CuO-Fe2O3-CeO2 catalyst, and improved the catalytic activity of the CuO-Fe2O3-CeO2 catalyst. The addition of CeO2 to CuO-Fe2O3 catalyst increased the amount of Lewis acid sites and Brønsted acid sites, and enhanced the acid intensity of the weak acid sites, which in turn promoted the catalytic performance of CO2 hydrogenation to DME. The optimal introduced amount of Ce in the catalyst was determined to be3.0 wt%. The CO2 conversion and DME selectivity were 20.9%, and 63.1%, respectively, when the CO2 hydrogenation to DME was carried out at 260°C, and 3.0MPa with a gaseous hourly space velocity of 1500mLgcat −1 h−1.
      Graphical abstract image

      PubDate: 2016-07-24T10:46:20Z
       
  • Electrochemical impedance spectroscopy for analyzing microstructure
           evolution of NaA zeolite membrane in acid water/ethanol solution
    • Abstract: Publication date: 22 October 2016
      Source:Chemical Engineering Science, Volume 153
      Author(s): Xianshu Cai, Yuting Zhang, Liangwei Yin, Dandan Ding, Wenheng Jing, Xuehong Gu
      NaA zeolite membrane exhibits high separation performance in dehydration of organics. However, the structural stability of NaA zeolite membrane is a critical issue for large-scale applications. In this study, electrochemical impedance spectroscopy (EIS) was first adopted to reveal the microstructure evolution of NaA zeolite membrane. Pervaporation separation of NaA zeolite membranes in acid water/ethanol solution was investigated for comparison. The permeation flux decreased initially and then increased while the separation selectivity declined continually. SEM, EDS and XRD characterizations showed structural degradation of NaA zeolite membrane layer in acid environments. Electrochemical impedance of NaA zeolite membrane was measured in acid solutions. The variation trend in the electrochemical impedance was found to agree well with that for separation performance caused by microstructure evolution. An equivalent circuit model was also constructed to evaluate electrical properties of the membrane system.
      Graphical abstract image

      PubDate: 2016-07-17T11:10:25Z
       
 
 
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